Resilience to forest fires and the role of landscapes

A prolonged fire season has underscored the need for continued vigilance in planning, preparation and maintenance.

From landscaping selection to vegetation management plans, managers must take positive steps to reduce the overall risk of forest fires for their facilities.

In 2021, more than 46,000 forest fires burned more than 5 million acres of land. Many of these fires occurred outside of the traditional fire season of September and October.

The extension of the fire season has underscored the need for continued vigilance with regard to planning, preparedness and maintenance of forest fire resilience by institutional and commercial facilities. Understanding the vulnerability of an installation goes beyond the building and its contents. It includes landscaping and landscaping around his property.

A building’s first line of defense against an approaching forest fire is its surroundings. The defensible space of a building is divided into three zones and is the area between a building and an approaching forest fire, where the facility’s maintenance team can manage vegetation and other combustible materials. in order to minimize the risk of ignition and the spread of fire.

The team must manage this space and its contents to maintain protection throughout the year. Landscaping with fire-resistant plants is key to dramatically reducing the risk of a forest fire for a facility, but there can be no assurance that this effort will eliminate all risks.

Ignition problems

Zone 1 is located within 5 feet of the building and is often referred to as the building ignition zone. The objective of activities in this area is to reduce the risk that the ignition of combustible materials by embers will cause the flames to come into direct contact with the building. Because this area is the closest to the building, it requires the most careful selection and intensive management of vegetation and materials. Managers should:

  • Install hard surfaces in this area, such as a concrete walkway, or use non-combustible mulch products, such as rock mulch.
  • Remove dead plant material from the vegetation.
  • Plant acceptable landscaping vegetation in this area, including an irrigated lawn and low-growing (non-woody) herbaceous plants. Shrubs and trees, especially evergreens, should not be used in this area, and vegetation that may overhang the roof can cause flammable debris to build up on the roof.
  • Limit the selection of plants to varieties that do not grow more than 12 inches in height if the facility has a non-combustible coating, such as fiber cement, and the decision is to have plants in that area. Workers should water and maintain the vegetation in this area as any plant can become highly flammable if it is dead, withered or poorly maintained.

Plants suitable for this area include creeping phlox, candy plants, and Mexican hens and chicks. It’s important to note that each of these plants thrives in USDA hardiness zones 9 through 11 and has a maximum height growth of 8 inches. For additional plants suitable for locations prone to wildfires, managers can consult the Insurance Institute for Business & Home Safety’s (IBHS) Wildfire Ready Landscaping Guide for Businesses.

Vegetation management

Zone two, located within 5 to 30 feet of the facility or property line, is where vegetation management is important to keep fire from climbing into the upper parts of trees or shrubs. and to prevent the fire from burning directly into the building. Trees and shrubs in this area should be in well-spaced, well-maintained groups.

Removing scale fuels that can allow fire from low vegetation to reach higher vegetation and creating separation between plants or groups of plants are effective techniques for achieving this goal. These techniques include:

  • Dead plant material and tree branches should be removed on a regular maintenance schedule.
  • Create islands or clusters of vegetation that will result in a discontinuous path of vegetation, which will prevent the fire from burning directly into the building. Embers could still ignite individual patches of vegetation in this area.
  • Remove lower tree branches and nearby shrubs (combustibles from ladders) so that a surface fire cannot reach the treetops. Trees located in this area must be maintained with a minimum horizontal spacing of 10 feet between crowns. Branches should be removed from the lower third of the height of the tree.
  • Paved parking lots surrounding commercial developments can act as a fire stop, preventing fires from burning directly into buildings. The building should always maintain design features that minimize vulnerabilities to exposure to embers.

Suitable plants in this area include brilliant blue agave, hosta lily, and solar roses. It’s important to note that each of these plants thrives in different USDA hardiness zones and has different maximum height growth, with the tallest measuring 36 inches.

Slow down the roller

Zone three, located within 30 to 100 feet of the building or property line, has the primary purpose of slowing the fire and reducing its energy. Maintenance tactics include:

  • The spacing of trees and brush should force the fire in the tops of trees or shrubs to fall to the ground.
  • Trees should be spaced at least 10 feet between the tops.
  • Tree branches should be pruned so that they do not hang less than 10 feet from the ground.
  • Dead trees, leaves and shrubs should be removed.

Appropriate landscaping in this area may include taller trees and shrubs. Some examples that are hardy in USDA hardiness zones 3 through 8 are Canadian red cherry, green ash, and Kentucky coffee.

In addition to selecting the appropriate landscaping, managers should consider developing a vegetation management plan that provides details and images on the topography – slope and aspect – location of buildings on the plot, details and location of the proposed fuel treatment, presence of noxious weeds on site and in the vicinity, sensitive environmental concerns – for example, threatened and endangered species, as well as sensitive species and state-listed wetlands – and vegetation maintenance and monitoring programs.

The plan should also provide information on how workers will develop and maintain the three defensible zones of space. Managers should incorporate the vegetation maintenance plan into their facility inspection and maintenance plans. IBHS recommends carrying out inspections at every change of season and after significant weather events.

From landscaping selection to vegetation management plans, managers must take positive steps to reduce the overall risk of forest fires for their facilities. Working with neighboring facilities can create a more resilient community. While managers can’t completely eliminate the risk of wildfires, together they can help reduce damage and overall business downtime.

Chris Cioffi is a sales engineer in the Insurance Institute for Business and Home Security.

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